The invention relates generally to agricultural machines and more particularly to a self-propelled agricultural machine having a tiltable steering column to which a gear-shift lever is selectively operatively attached.
A multi-stage gearbox is a necessary requirement in self-propelled agricultural machines since the speed of travel is appreciably less when working in the field, such as harvesting, than when running on a highway. The gearbox forming the main drive mechanism normally comprises at least two forward gear stages in addition to a reverse gear stage. These three functions are accessible via a shift lever and a gear-shift-transfer element of the gear box coupled thereto. A rod-linkage assembly, an actuator link or a hydraulic device are suitable for the gear-shift-transfer element. The shift lever is coupled to the input member of the gear-shift-transfer element irrespective of the particular arrangement being used. The gear box is equipped with a slidable shaft on which the relevant gears are moved during a gear change. These gear shifts are effected while the machine is stationary and the speed of travel is regulated by a hydraulic drive arrangement when in either of the two gear stages. In harvesting machines known up to now, the manual shift lever was located in the cab adjacent the operator's seat.
A steering column supporting the steering wheel can be adjusted through a predetermined angular range both forwardly and backwardly in relation to the direction of travel of the agricultural machine so that each operator can set the steering wheel to the most comfortable position. For this purpose, the steering column is constructed as a single unit or consists of several mutually articulated sections. The base portion of the steering column is articulated to the floor of the operator's cab. Locking and releasing devices are provided near the pivotal point in both the single and the multi-section assemblies. These devices, in the form of hand or foot operated levers, are operable from the cab to actuate a control element in the form of a lockable gas strut, for example. In these known arrangements, the number of actuating elements in the cab has been found to be disruptive since they limit the operator's freedom of movement.
A steering device for a self-propelled combine harvester is known from DE 1755309 A1. This includes a joystick which is not used for steering the combine harvester but is connected to a control device so that e.g. the speed of travel of the combine harvester will be altered if the joystick is tilted in the direction of travel. In this case, the joystick is effective on a hydraulic device to alter the speed of travel of the combine harvester in a continuous manner should a sweeping motion occur in the direction of travel or vice versa. This document provides no insight about the operation of a mechanical gear box.
An object of the present invention is to provide a self-propelled agricultural machine in which the gear shifting function will be ensured in a simplified manner.
Another object is to provide a self-propelled agricultural machine having a gear shifting function but with reduced number of operating devices.
Yet another object is to provide a machine in accordance with the foregoing objects without limiting the ease of operation of the machine by overloading the driving position with operating devices of different sorts.